Multi-dosage jet injector



Sheet of 2 Feb. 4, 1969 R. R. STEPHENS MULTI-DOSAGE JET INJECTOR med April 2e, 196e Feb. 4, 1969 Sheet Filed April 26, 1966 j, kkww/w/MH Y y I Q n@ QQ QN A 66N N Y@ j 11 l l t l fr., f1 l@ j l /MQ/ /Q/Q \\\N\ United States Patent Office 3,425,413 Patented Feb. 4, 1969 9 Claims ABSTRACT F THE DISCLOSURE A jet injector having a reciprocatory mount for a reservoir of liquid to Vbe injected and driven means being connected with the mount for imparting a rectilinear drive stroke and return stroke thereto. Means are provided to releasably secure a reservoir of injection liquid to the mount and a plunger carried lby the mount is arranged for communication with the liquid. A cylinder in which the plunger is received for the expulsion of liquid therefrom on a drive stroke of the plunger is provided and a first-way valve is located to prevent return of liquid from the cylinder to the plunger on the drive stroke thereof. A mount for a nozzle communicates with the cylinder for receiving liquid expelled therefrom and a second one-way valve serves to prevent the ingress of air into the cylinder on a return stroke of the plunger.

This invention relates to injection devices intended for the hypodermic introduction of for example anaesthetics without the use of a needle for perforating the skin.

Injection devices of this kind, generally referred to as jet injectors, are finding increasing use but their application has been limited in some degree by the difficulty which has been experienced in providing for the necessary high thrust of liquid jet needed to perforate the skin without resorting to heavy and cumbersome machinery. Such jet injections as have found successful realization in the past have been more appropriate to veterinary use.

An additional complication in the construction of jet injectors has arisen from the need to make some provision for varying the dose of anaesthetic or whatever other liquid may be injected, and in the past those constructions which have been proposed involve the provision of suicient power to deliver the maximum dose which might ordinarily be required. Variation in dose has then simply involved the incorporation of some means for limiting the stroke of the plunger which pressurizes and expels the liquid. Yet an additional complication has arisen from the desire to provide some form of automatic recharging mechanism so that the liquid to be injected can be withdrawn automatically from a reservoir carried by the injector instead of having to furnish a fresh cartridge or the like each time an injection is to be made.

It is an object of the invention to provide a jet injector suitable for, inter alia, dental use which is comparatively lightweight and will yet provide for an injection of a range of doses of anaesthetic. Another object of the invention is to provide a new and improved construction of jet injector wherein the mechanism for withdrawing successive charges of liquid from a reservoir carried by the injector is greatly simplified. Another object is the provision of a jet injector which may be light in weight and of small size `but which can nevertheless be operated directly from a source of pressurized air such as is ordinarily available in a dental surgery, for example 40-60 pounds per square inch.

The invention consists broadly in a jet injector comprising a reciprocatory mount for a reservoir of liquid to be injected, driven mechanism connected with said mount to impart a rectilinear drive stroke and return stroke thereto, means for releasably securing a reservoir of injection liquid to said mount, a tubular plunger carried by the mount arranged to communicate with liquid in the reservoir which will be carried by said mount, a hydraulic cylinder in which said tubular plunger is slidatbly received for the expulsion of liquid therefrom on a drive stroke of said plunger, a first one-way valve located to prevent return of liquid from said cylinder to the reservoir on a drive stroke of the plunger and a second one-way valve located to prevent the ingress of air into Said cylinder on a return stroke of said plunger.

Two types of construction are contemplated in accordance with the present invention but each is characterized by the novel feature described in the foregoing paragraph, of having the reservoir for the liquid to be injected mounted to move as one with the plunger of the hydraulic cylinder from which the liquid to be injected is expelled through the injector nozzle. In the first type of construction, the just-mentioned hydraulic cylinder is fixed. In the second type of construction, the hydaulic cylinder referred to is slidably received in a second, larger hydraulic cylinder with the rst hydraulic cylinder and the tubular plunger moving together as one after the latter has described an initial part of its drive stroke. In this second arrangement, the resulting jet is characterized by an initial pilot jet serving to perforate the skin in a by now well known fashion `which is then followed by a main jet of liquid which passes through the resulting perforation. Any convenient stop mechanism can |be used to engage the first hydraulic cylinder and drive it forward when required; t-hus it may be engaged by the mount for the reservoir which carries the tubular plunger.

The mount for the reservoir will normally have the form of a boss through which passes a tubular needle and the rear end of which serves to perforate, establish communication with and secure a cartridge of liquid to be injected while the forward end serves as tubular plunger. The one-way valve serving to close the tubular plunger on a drive stroke thereof may take the form of a peg itted in the forward end of the plunger; if desired, this may be associated with a return spring although in the case of a captive peg, inertia and back pressure may be relied upon.

It is preferred that the mount for the liquid reservoir should `be received in a guide sleeve serving to guide the mount and/or liquid reservoir. To establish a drive connection to the mount, this guide sleeve may be slotted and an attachment means may then pass through the slot or slots from an outer drive member. This outer drive member may itself be tubular and may be for example bolted to the reservoir mount.

The drive mechanism for the reservoir mount preferably comprises a pneumatic cylinder and piston. This may be provided towards the rear end of the injector and the pneumatic piston may have a tubular skirt arranged to transmit thrust to the reservoir mount. In one convenient arrangement, this tubular skirt slidably receives and abuts the aforementioned drive member. The latter and the pneumatic piston may have respective return springs.

For convenience in handling the injector, it has Ibeeu found preferable to mount a button actuated or like pneumatic valve at the rear end, that is to say, the end remote from the jet injector nozzle. This valve will normally incorporate or rbe closely associated with the inlet attachment for compressed air as Well as an appropriate exhaust outlet. A button actuated spool valve is preferred, open to exhaust in its neutral undepressed position. To provide for a snap actuation of the pneumatic valve, a spring may be interposed between the press button or other manual actuation member, and the valve, in association with means for abruptly releasing the valve to admit compressed air when the spring pressure reaches a predetermined minimum. The release means may comprise a spring-loaded ball engaged in a detent in a valve member to be moved by operation of the manual actuation member. The valve member just referred to will be the spool in the case of a spool valve. This arrangement ensures that the valve is opened abruptly even when the press button is operated slowly.

A distinct feature of the present invention is the means for varying the dose of liquid to be injected. Instead of providing for a maximum dose and progressively smaller doses, it is preferred to construct an injector instead to deliver a predetermined comparatively small dose and have an automatic recharging mechanism so that larger doses can be given simply by repeating the original small dose. This departure from what has hitherto been standard practice in this field is an important factor in enabling the injector to be constructed in a small, lightweight forrn while being capable of operation by the comparatively low air pressures such as are normally available in a dental surgery. Thus, in this aspect, the invention comand piston for the delivery of a small fixed predetermined dose and means for automatically recharging the cylinder after a dose has been ejected therefrom. The fixed predetermined dose is preferably no greater than 0.015 ml.

In a modification, a jet injector constructed to give a fixed predetermined repeated dose of liquid in the form of a pilot jet and a succeeding larger jet incorporates stop means whereby the pilot jet only may be given when desired. In this way, the pilot jet may itself be treated as a small fixed dose and doses smaller than the full dose delivered by the jet injector may then be given as a rapid succession of pilot doses.

The invention will be described further with reference to the accompanying drawings, of which:

FIGURE 1 is a longitudinal sectional view of one embodiment,

FIGURE 2 is a longitudinal sectional view of a second embodiment, and

FIGURE 3 is a longitudinal sectional view (on a larger scale) of a detail of FIGURE 2.

Referring first to FIGURE 1, the injector comprises a tubular body 1 housing at its forward end a hydraulic cylinder 2 which communicates at its forward end with a detachable jet nozzle 3 by way of a one-way valve 4 associated with a return spring 5. The nozzle 3 is retained in position by a screw cap 6 and of course, any desired form of nozzle may be employed. The nozzle terminates at a fine jet orifice 7 through which the injected dose will emerge at high velocity.

At the other end of the body 1 is a pneumatic cylinder 8 housing a pneumatic piston 9 behind which is fitted an inlet/exhaust valve 10. The piston 9 carries a tubular skirt 11 associated with a return spring 12. The tubular skirt 11 slidably receives a guide tube 13 which is in the form of a rearward extension of the hydraulic cylinder 2 and is intended in turn slidably to receive a cartridge (not shown) of liquid to be injected.

To carry the cartridge, there is provided a mount 14 in the form of a boss sliding within the guide tube 13. Although not apparent in the illustrated view, the guide tube 13 is longitudinally slotted and through the slots, a tubular drive member 15 which is slidably received on the outside of tube 13, is engaged to the mount 14. The tubular drive member 15 has its own return spring 16. A tubular needle 17 passes axially through the reservoir mount 14 and is sharpened at 18 at its rear end to perforate a rubber bung conventionally provided on a cartridge of anaesthtic. The tubular body 1 of the injector is made in two parts which detachably engage at a screw or bayonet filling 19 so that the injector may readily be taken apart for loading. When taken apart, the injector may then be loaded by sliding a cartridge of anaesthetic down the guide tube 13 so that the rubber' bung at its forward end is perforated `by the tubular needle 17 which serves to hold the cartridge on the mount 14 as well as establishing liquid connection with the interior of the needle 17. The injector may then be reassembled.

At its forward end, the needle 17 is furnished with a one-way valve in the form of a peg 20 having a return or valve spring 21 urging the peg in a direction to close the forward end of the needle 17.

In the illustrated construction, provision is made for a first, high velocity stage injection of liquid but mention may now be made of the fact that the forward portion of the needle 17 could quite well serve directly as the hydraulic plunger for the hydraulic cylinder 2. In this case, the cylinder 2 would have a correspondingly narrow bore and 'upon a forward stroke of the pneumatic piston 9, a single small dose would be injected, the skirt 11 of the piston 9 abutting directly against the rear end of the tubular drive member 15.

Instead of, however, as illustrated, the forward end 22 of the needle 17 is received in a first or intermediate hydraulic cylinder 23 which is in turn slidably received in the hydraulic cylinder 2 and serves as the hydraulic plunger therefor. The intermediate hydraulic cylinder 23 is guided in the guide tube 13 and at its rear end 24 is engaged by the reservoir mount 14 after the latter has described an initial part of its forward drive stroke.

In operation, as the piston 9 moves forward the skirt 11 drives the tubular drive member 15 which carries with it the reservoir mount 14 and thus propels the forward part 22 of the needle 17 within the hydraulic cylinder 23. Since the valve 20 will now be closed by a cornbination of inertia, pressure of spring 21 and hydraulic pressure, this movement causes the expulsion of liquid through the jet orifice 7, it being assumed that the injector is already primed by the cylinders 2 and 23 being charged with liquid from a previous operation. As soon as the receptacle mount 14 engages the rear end 24 of the cylinder 23, the latter itself is forced to move forward within the hydraulic cylinder 2 and having of course a larger cross section than the needle 17 causes liquid to be ejected through the orifice 7 at a lower pressure.

The inlet/exhaust valve assembly 10 comprises a valve button 25 engaged with a spool 26 having a restricted neck 27 which in the released position of the button 25 under the iniiuence of the return spring 28 serves to establish an exhaust connection from the rear of the piston 9 through a passageway 29 leading past the neck portion 27 to an exhaust outlet passageway 30. When the button 25 is depressed the outlet to the passageway 30 is immediately closed and on further depression the neck portion 27 enters an inlet passageway 31 thus establishing a connection from a compressed air inlet 32 through to the passageway 29. The return spring 12 serves to return the piston 9 whilst the separate return spring 16 returns the drive ring 15 and with it the reservoir mount 14. On a return stroke of the latter due to the closing of the oneway valve 4, the one-way valve 20 is sucked open and the cylinders 2 and 23 are recharged from the reservoir.

The piston 9 also carries a guide skit 33 which is slidably received in the tubular body 1. This guide skirt 33 is longitudinally slotted at 37 with the slot cooperating with a peg 38 constraining the skirt 33 against rotation. At a circumferentially displaced position, the guide skirt 33 is formed with a stepped slot 39 which cooperates with a circumferentially displaceable peg 34 for the purpose of regulating the output dose. The peg 34 is for this purpose carried by a rotary ring 36 so that it can be turned as desired from one extreme position in which it will permit the plunger to move forward for its full stroke, to the other extreme position in which it will if desired obstruct the guide skirt 33 at its forward end, thus limiting the stroke of the piston 9 to such an extent that the reservoir mount 14 moves forward sufficiently only to give a pilot jet injection without engaging and moving the intermediate hydraulic cylinder 23. Steps in the slot 39 may provide for intermediate doses through correspondingly positioning the ring 36. The peg 34 protrudes through -a slot 35 in the tubular body portion 1, while the ring 36 is located at predetermined rotational positions by means of a ball 40 which is biased by a spring ring 41 to engage in spaced recesses 42 in the body portion 1.

To avoid a oating action of the cylinder 23 and to ensure that the needle 22 does not pull out of it on a return stroke, appropriate stops or the equivalent will be provided. Thus, the cylinder 23 may have a return spring 23a and the sleeve 13 may have a lining 13a located to serve as a stop against which the cylinder in its rest or starting position is pushed by its spring 23a.

In FIGURES 2 and 3, a simplified version of the injector is illustrated, having only one stage of injection. In these figures, corresponding pats have the same reference numerals as in FIGURE l, and the description which follows will be confined mainly to those features which are different.

The basic difference is that the cylinder 23 is omitted, while the driving sleeve is also omitted, with the tubular skirt 11 being connected directly to the mount 14 by the lugs 43 passing through slots 44 in the sleeve 13. Because of the omission of sleeve 15, the tubular skirt 11 is no longer clamped in the pneumatic piston 9, but is detacha-ble therefrom, to permit opening of the injector at the point 19 for reloading purposes. The spring 16 thus becomes the return spring 12 for skirt 11, while the piston 9 now has its own return spring 12a within the cylinder 8. A stop collar 45 in cylinder 8 determines and limits the stroke of the piston 9 by engagement with a suitably faced forward end 46 of the piston.

The peg is shown in greater detail in FIGURE 3. It comprises a tube 47 the bore of which stops short of its forward end 48 which is threaded to carry a nose 49. The rear face of this nose is counterbored to receive a polytetrafluorethylene ring 50 just behind which is a transverse outlet 51 from the tube 47. At its other, rear end, the tube 47 is counterbored and threaded to receive a tubular head 52. The latter serves to retain the tube 47 in the tubular needle 17 with some degree of lost motion, by engaging a sleeve 53 welded into the forward end portion of needle 17. The degree of lost motion of the captive peg 20 is enough to uncover the outlet 51 when the nose 49 is pulled forwardly by hydraulic tension. On the other hand, when the needle 17 is driven forwardly, hydraulic pressure and inertia are sufiicient to push the peg 20 back so that a forward extremity 54 of the needle 17 seals against the ring 50. The return spring 21 (FIGURE l) is found not to be required.

The remaining principal digerence concerns the pneumatic valve 10. Here, the button has been separated from the valve spool 26 and a compression spring 55 inserted between them. Further, the spool 26 is formed with an annular recess or detent 56 in which a ball 57 engages under pressure from an associated spring 58. When the spring 55 is compressed by pressure on button 25, a forward thrust is transmitted to spool 26. When this thrust is high enough to lift the ball 57 out of the recess 56 the spool will jump forwards to open the valve 10.

The nozzle 3 is slightly different in that it can now be unscrewed from the cap 6 which houses the valve assembly 4, 5.

The stroke of the injector illustrated in FIGURES 2 and 3 is short, and injections can lbe given in very rapid succession. Preferably, the parts are dimensioned so that each dose is not greater than 0.02 ml. suitably 0.015 ml. or less, though not normally below .005 ml. Greater doses can then be administered as a succession of these small doses. The reservoir of liquid to `be injected, in the form of a standard cartridge of glass or transparent plastic material, will be located generally as indicated by a dotted outline 59 in FIGURE 2, it being understood that its length may vary. The tubular skirt or sleeve 11 may be slotted along opposite sides to enable the cartridge to be grasped for withdrawal when empty. The outer case 1 may also be windowed or apertured, as well as the sleeve 13 at 60, for sighting purposes.

I claim:

1. A jet injector comprising a reciprocatory mount for a reservoir of liquid to be injected, driven mechanism connected with said mount to impart a rectilinear drive stroke thereto, means for releasably securing a reservoir of injection liquid to said mount, a tubular plunger carried by said mount arranged for communication with liquid in the reservoir which will be carried by said mount, a hydraulic cylinder in which said plunger is slidably received forthe expulsion of liquid therefrom on a drive stroke of said plunger, a first one-way valve located to prevent return of liquid from said cylinder through said tubular plunger on a drive stroke of said plunger, said first one-way valve comprising a peg captively mounted in a free end of said tubular plunger having a degree of axial lost motion permitting relative motion of the peg to open and close said plunger, a mount for a nozzle communicating with said cylinder to receive liquid expelled therefrom, and a second one-way valve located to prevent the ingress of air into said cylinder on a return stroke of said plunger.

2. The jet injector according to claim 1 wherein said peg comprises a tubular body within said plunger, a head of greater diameter than said body outside said plunger, and an outlet from said tubular body adjacent said head.

3. A jet injector comprising a reciprocatory mount for a reservoir of liquid to be injected, driven mechanism connected with said mount to impart a rectilinear drive stroke and return stroke thereto, means for releasably securing a reservoir of injection liquid to said mount, a tubular plunger carried by said mount arranged for communication with liquid in the reservoir which will be carried by said mount, a first hydraulic cylinder in which said plunger is slidably received for the expulsion of liquid therefrom on a drive stroke of said plunger, a first one-way valve located to prevent return of liquid from said cylinder through said tubular plunger on a drive stroke of said plunger, a second hydraulic cylinder in which said first hydraulic cylinder is slidably received and which communicates therewith for the expulsion of liquid therefrom on a drive stroke of said first hydraulic cylinder, means for driving said first hydraulic cylinder and plunger forwardly as one when said plunger has performed a predetermined fraction of its drive stroke. means for subsequently returning the first hydraulic cylinder to a starting position, amount for a nozzle communicating with said second hydraulic cylinder to receive liquid expelled therefrom, and a second one-way valve located to prevent the ingress of air into said second hydraulic cylinder on a return stroke of said first hydraulic cylinder and of said plunger.

4. The jet injector according to claim 3 wherein the means for driving said first hydraulic cylinder comprises mutually engaging portions of said first hydraulic cylinder and said reciprocatory mount.

5. The jet injector according to claim 1 wherein said driven mechanism comprises a pneumatic ram and cylinder and a tube driven by said ram embracing and linked to said reciprocatory mount, said tube being separable from said ram to permit positioning and withdrawal of an injection liquid reservoir, and said tube extending substantially beyond said mount to embrace a mounted injection liquid reservoir lbeing slotted to permit said reservoir to be grasped for withdrawal.

6. The jet injector according to claim 3 incorporating retractable stop means for limiting the stroke of said mechanism to not more than said predetermined fraction whereby movement of said second hydraulic cylinder is avoided.

7. The jet injector according to claim 6 wherein the stroke of said mechanism when limited by said stop means corresponds to an expulsion of from 0.005 to 0.015 ml. of

liquid by said tubular plunger.

8. The jet injector according to claim 1 wherein said driven mechanism comprises a pneumatic ram and cylinder, said ram having a cylindrical skirt, said skirt being formed with an axially stepped slot, said injector further comprising a stop member `arranged to extend into said slot, and means for positioning said stop member and skirt circumferentially relative to one another whereby different chosen steps in said slot can be caused to engage against said stop member on a forward, driven stroke of said ram.

9. The jet injector according to claim 3, wherein said driven mechanism comprises a pneumatic ram and cylinder, said ram having a cylindrical skirt, said skirt being formed with an axially stepped slot, said injector further comprising a stop member arranged to extend into said slot, and means for positioning said stop member and skirt circumferentialiy relative to one Vanother whereby diierent chosen steps in said slot can be caused to engage against said stop member on a forward, driven stroke of said ram.

References Cited DALTON L. TRULUCK, Primary Examiner.

MARTIN F. MAJESTIC, Assistant Examiner. 

